Second anode contact for cathode-ray tubes



March 7, 1950 PHELPS 2,499,834

SECOND ANODE CONTACT FOR CATHODE-RAY TUBES Filed Sept. 24, 1946 Zhmentor George NPkel bs Patented Mar. 7, 1950 SECOND ANODE CONTACT FOR CATBODE- RAY TUB George N. Phelps, Lancaster, Pa., assignor to Radio Corporation of America, a corporation oi. Delaware Application September 24, 1946, Serial No. 699,047

6 Claims.

My invention relates to electrical contacts of the type consisting of a metal cup embedded in the wall of the glass envelope of electrical discharge devices, such as cathode ray tubes, with its rim practically flush with the outer surface of the wall to permit electrical connection to be made to an electrode inside the envelope by a connector clip inserted in the cup.

In some types of cathode ray tubes an electrode, such as the second anode, is a conductive coating on the inner wall of a glass envelope or bull; exhausted to a very good vacuum. Voltage is applied to this electrode or second anode through a cup type electrical contact or second anode contact embedded in and extending through the glass wall and electrically connected to the second anode. The contact must make a permanent substantially strain free fused seal with the glass, as it is a part of the wall of the highly evacuated bulb, and good firm electrical contact must be maintained between the contact and the con.- nector or clip which supplies the voltage. The contact must be so made that the stresses and strains produced by the insertion and removal of the connector will not distort the contact or overstrain the fused seal or junction between the contact and the glass wall of the bulb.

A principal object of my invention is to provide an improved electrical contact suitable for cathode ray tube second anode contacts and similar purposes, by which improved electrical connection to the voltage cable connector is obtained.

Another object is to provide a simpler second anode contact which is easier to make and is cheaper than the contacts heretofore used, and in which leaks due to cracks in the metal from overworking and to defects arising from the manufacturing operations are minimized.

A further object is to make the surface of the contact which is exposed to the inside of the cathode ray tube of such shape as to eliminate all recesses in which water from washin and otherwise treating the tube may collect.

My invention will best be understood in connection with the accompanying drawing in which merely for purposes of illustration I have shown a preferred embodiment of m invention and in which Fig. 1 is a plan view showing my improved contact in place in the wall of the bulb;

Fig. 2 is a longitudinal section of the contact; and

Fig. 3 is a longitudinal section along the line 3-3 of Fig. 1 showing the contact in section and in addition a resilient member for improving the electrical connection between the contact and the conductive coating on the inner wall of the bulb, and also showing one form of connector clip or terminal inserted in the cup shaped contact to supply voltage to the conductive coating.

Referring to the drawing, I0 is a portion of the glass wall of an electrical device, such as a cathode ray tube, in which a contact made in accordance with my invention is embedded to constitute a second anode contact. As best shown in Fig. 2, my improved contact is essentially a drawn cup ll of a metal or alloy having such properties and coeificient of thermal expansion as to secure a seal to the glass of the bulb of the tube and preferably having the same coeflicient of thermal expansion as the glass. The cup is preferably drawn from sheet metal in dies by several steps or draws, and its shape, as shown in Fig. 2, is such that the metal is not over-worked during the drawing and hence does not develop weaknesses or cracks. The thin peripheral wall I2 of the cup flares outwardly, preferably at an angle of about 30 degrees, and is inturned at its upper edge to form a rounded rim I3 and a narrow flange It. A flat insert ring l5, extending radially inward at the top of the cup, preferably of the sam metal as the cup and of the same thickness as the wall I! of the cup, is seated firmly in the cup near the top and immediately beneath the flange it. The flat insert ring I5 is of substantially the same diameter as the inner diameter of the cup near the rim so that the edge of the insert ring seats firmly on the flaring wall of the cup which in effect forms a shoulder for the ring, and is held firmly in place by the flange I4. The radius of curvature of the rounded rim l3 does not produce a sharp edge on the outside of the rim, and is small enough to hold the ring absolutely tight in the cup. The insert ring is preferably provided with a lip l6 tapered to fit snugly in the cup and to rest on the flaring wall l2 near the top of the cup.

The contact is sealed into and forms part of the wall of the evacuated bulb and must be imperforate and gas-tight. The cup H has an imperforate bottom which may be fiat and substantially flush with the inner surface of the bulb wall, or for some types of tubes may to advantage have a stud projecting into the interior of the bulb. In accordance with my invention, the bottom wall of the cup may be drawn to produce an integral tubular stud or projection H in the form of a right cylinder with a rounded end, and extending outwardly from the interior of the cup. It has been found that such a tubular stud ll of I! may be roughened, preferably by means of shallow depressions or notches I! produced by knurling or rolling. As best shown in Fig. 3, a speed nut IS in the form of a resilient strip may he slipped over the stud II to bring its ends into yielding but firm engagement with the inner conductive coating or second anode 20, and is held in position by the notches I8, 'as indicated in 3. t has been found that the cup illustrated in cup and hold the projections on the arms 22 firmly against the insert ring when the clip is in the contact.

My improved contact will make with the glass commonly used for bulbs .a hermetic fusion seal which is permanent and practically free from defects and strains. The contact is simple and cheap to manufacture as it can be made by drawing sheet metal into the desired form without over-stressing or over-working the metal, provides ample area for a good electrical connection to Fig. 2, but without the insert ring and made with only an inturned flange about as wide as the insert ring, cannot withstand without injury to the seal the stresses and strains which occur during normal uses of the tube and to which it is subjected by the insertions and removal of the voltage connector clip. It has also been found that it is not feasible to clamp the ring in place in the cup by crimping the rim of the cup down on both sides of the edge of a flat insert ring, as three thicknesses of metal at the rim of the cup set up severe strains in the seal to the glass and result in leaks and cracks. It is therefore necessary to hold the insert ring solidly in place near the rim of the cup without there being more than two thicknesses of metal at the rim.

The principal part of the seal between the contact and the glass of the bulb is made along the flaring wall of the contact, and experience has shown that abetter and more permanent seal is obtained between the glass and flaring wall of the contact than can be obtained when the cup is a right cylinder with straight walls. Sealing of the contact into the bulb wall is facilitated by beading the rim 13 with a thin layer of glass and, as shown in Fig. 3, the glass of the bulb wall may to advantage be brought up over the rounded rim H3.

There are many alloysand metals such as alloys of chromium and iron containing 25% to 30% chromium, and alloys of chromium, iron and nickel which have the properties and coefiicient of thermal expansion such as to secure a seal tothe glass commonly used for the bulbs of electrical discharge devices. A contact drawn from a sheet about .012 inch thick of an alloy of nickel, chromium and iron containing about 42% nickel, 8% chromium and the balance iron has been found to be satisfactory. This alloy is available on the market and is described more in detail in U. S. Patent 2,394,919, Kingston. The contact is made by drawing the sheet metal in a series of steps into the cup shape shown in the drawings. In a second anode contact of suitable size for cathode ray tubes the cup is about 0.6 inch in diameter at the top, about 0.2 inch deep, the flange I about 0.05 inch in width, the opening in the insert ring about 0.3 inch in diameter, and the tapering lip IS on the edge of the ring about 0.06 inch wide. If the tubular stud i1 is used, it projects from the bottom of the cup about 0.25 inch and has a diameter of about 0.16 inch.

A firm electrical connection to the contact may be made by some form of connector clip such as shown in U. S. Patent 2,270,337, Pensak, or preferably by a connector clip which firmly engages the bottom of the cup and also the underside of the insert ring. Merely for purposes of illustration, Fig. 3 shows a spring clip comprising a metal disc 2| having spring arms 22 with projections or bends for engaging the insert ring [5 and the connector clip for supplying voltage, and is mechanically strong enough to resist deformation and injury to the seal between the walls of the contact and glass of the bulb.

What I claim is:

1. An electrical terminal connector for electrical discharge devices comprising a metal cup having an imperforate bottom wall and a thin peripheral wall of metal adapted to seal to glass and forming an inwardly extending shoulder near the rim of said cup, and a flat metal insert ring seated in and extending transversely-of the cup with its outer edge seated on and in firm engagement with said shoulder on said wall near the top of the cup, the rim of said cup being inturned over the edge of said ring and forming an annular flange in firm engagement with said ring and locking said ring in place in said cup.

2. An electrical terminal connector comprising a hollow body member having a conical wall section, a hollow stud formed as an integral portion of said conical wall section and closing one end thereof, said hollow stud extending outwardly from said body member, a ring-shaped wall portion fixed to and partially closing said other end of said conical wall section.

3. An electrical contact adapted to be sealed into and extend through a. glass wall of an electron discharge device to make electrical connection to an electrode inside the device and comprising an imperforate cup with an outwardly resilient ends 23 which rest on the bottom of the flaring thin wall of metal having a thermal expansion adapted to secure a seal with glass and a flat insert ring of the same metal as said cup having an outer diameter substantially equal to the diameter of said cup a short distance below its top and seated firmly on the flaring wall of the cup, the rim of said cup being inturned over the outer edge of said ring and forming an integral narrow annular flange extending radially inward of said cup and holding said ring firmly seated in the cup.

4. An electrical terminal connector for electrical discharge devices having a glass envelope comprising an imperforate cup of sheet metal having a thermal expansion adapted to secure a seal with glass and with an outwardly flaring wall rounded inwardly at the rim forming an annular flange concentric with and having an opening smaller than the to of said cup, and a flat metal ring seated in said cup immediately beneath said flange with its edge seated on said flaring wall and locked against said wall by said flange.

5. A contact terminal adapted to be sealed into a glass wall of an electron discharge device and comprising an imperforate metal cup with an outwardly flaring thin wall of metal having a thermal expansion adapted to secure a seal with glass, and a fiat insert ring of the same metal as said wall and of substantially the inner diameter of said cup near its top and having on its edge a lip tapered to fit into said cup near its top, the rim of said cup being rounded inwardly over 5 the edge ofsaid ring and holding said ring firm- 1y seated ons'aid flaring wall 01' the cup.

6. A gasetight envelope having a glass wall and enclosing an electrode, a contact terminal sealed into and extending through said glass wall to make electrical connection to said electrode, said terminal comprising a thin walled imperforate cup of metal having thermal expansion adapted to secure a seal with glass and sealed into and embedded in said glass wall with its rim below the outer surface of the surrounding glass, and a that insert ring of the same said metal seated in said clip with its edge secured to the wall of said cup near its rim. GEORGE N. PHELPS.

6 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

